We present enhancements for UDDI / DAML-S registries allowing cooperative discovery and selection of Web services with a focus on personalization. To find the most useful service in each instance of a request, not only explicit parameters of the request have to be matched against the service offers. Also user preferences or implicit assumptions of a user with respect to common knowledge in a certain domain have to be considered to improve the quality of service provisioning. In the area of Web services the notion of service ontologies together with cooperative answering techniques can take a lot of this responsibility. However, without quality assessments for the relaxation of service requests and queries a personalized service discovery and selection is virtually impossible. This paper focuses on assessing the semantic meaning of query relaxation plans over multiple conceptual views of the service ontology, each one representing a soft query constraint of the user request. Our focus ...